Saint Michael was the archangel who led God's army against the rebel angels led by Lucifer and cast them out of heaven. In paintings he is often shown in armour, defeating the devil. He is also sometimes shown holding a set of scales in which he weighs human souls as here in Crivelli's painting of him.

The fight between Saint Michael and the devil in the form of a dragon appears in the book of Revelations at the end of the Bible. Although only a short passage, it was an episode that caught the medieval imagination, and Saint Michael and the devil (often in the form of a dragon) became a popular subject for paintings.